Search for viral antigens as systemic diagnostic indicators of the presence of tumor(s); specifically: continue the isolation, purification, and physico-chemical characterization of sufficient quantities of the pertinent human antigen found in the 47D cell line (antigens from other human breast cancer cell lines should also be studied); conduct comparative biochemical studies of the human antigen and MuMTV gp52; and study the distribution of the gp52-related antigen in human mammary tumors as a function of geography, family history, and/or ethnic groups.